You're confusing two different technologies. TrueHD is a lossless data-packing alogrithm that stores information in a smaller space. Pro Logic II is surround processing that scales 2 channels to 5 speakers. One isn't at odds with the other; in fact, they can be used together.
It's like comparing eggs to frying. They're two different things. One isn't at odds with the other; in fact, they can be used together (you can fry an egg, just as you can apply PLII to a TrueHD soundtrack).
Frying an egg doesn't mean the result is no longer an egg. Applying PLII to a TrueHD soundtrack doesn't mean it is no longer lossless (any more than applying bass management or time alignment does).